1. Field of the Present Invention
The present invention relates to a monochromatic or multi-color recording material enabling a variety of light sources emitting light rays covering ultraviolet to infrared regions to be used and a photopolymerizable composition to be used for the material, more particularly a photopolymerizable composition with improved sensitivity, storage property, and photo fixation property and a recording material using the composition.
2. Description of the Related Art
Before, a variety of investigations of a dry type image recording method without using any developer liquid or the like and free from waste generation has been performed and among them, a method using a composition curable by light has drawn attention.
In such a method, a latent image is formed by exposing to light a composition, which is contained in a recording material and cured by light, and by curing it. On the other hand, a color image is formed due to the transfer of a component in unexposed areas, which affects coloration or decoloration reaction by heating, whthin the recording material. In the case of using such a recording material, at first, exposure is carried out by radiating light to the recording material through an image manuscript, a latent image is formed by curing the exposed areas, and then a visible image is formed by heating the recording material and by transferring the component in the un-cured areas (the un-exposed areas), which affects coloration or decoloration reactions, within the recording material.
By this method, a completely dry system free from waste generation can be achieved.
As the recording material to be employed for the above-described process, substantially, there are several types and they can characteristically be employed for black and white image recording process, yet they are especially advantageous for color image recording. As a specific recording material, for example, a two-component type photosensitive and heat sensitive recording material disclosed in Japanese Patent Application Laid-Open (JP-A) No. 52-89915 is known. The material is a heat sensitive recording material using, as the two-components, for example, an electron-accepting compound and an electron-donating colorless coloring material and containing a photo-curable composition inside or outside or both of microcapsules.
However, this recording material cannot sufficiently suppress the coloration in the cured areas even if the photo-curable composition contained in the microcapsules is sufficiently cured. Therefore, non-image areas are colored and the contrast tends to be decreased.
As a recording material free from coloration in the non-image areas, for example, a recording material is known which is disclosed in JP-A No. 61-123838 and has a layered structure comprising a layer of a photopolymerizable composition containing an acidic group-containing vinyl monomer and a photopolymerization initiator, an isolation layer, and a layer of an electron-donating colorless coloring material.
In the case of this recording material, the non-image areas, that is, the areas cured by photopolymerization reaction, have no heat diffusion property of the acidic group and are not colored. However, on the other hand, it has a disadvantage that the coloring density itself is slightly low.
Also, as a negative type recording material image using a similar image forming method, there is a recording material disclosed in JP-A No. 60-119552. It is a recording material in which a photopolymerizable composition containing a monomer or a prepolymer for bleaching a coloring material and a photopolymerization initiator is isolated from a coloring material to be bleached. Similarly to the above-described recording material, this recording material also has a disadvantage that the coloring density is slightly low, although the non-image areas are not colored.
Present inventors, taking account of the above-described disadvantages, have proposed recording materials before, disclosed in JP-A Nos. 3-87827 and 4-211252, as recording materials capable of decreasing the coloration in the non-image areas and obtaining a high image density. The former recording material is a photosensitive and heat sensitive recording material which comprises one of the two color forming components which is encapsulated in microcapsules and the other as a curable compound of a photo-curable composition or the other together with a photo-curable composition outside the microcapsules. On the other hand, the latter recording material is a photosensitive and heat sensitive recording material which comprises a layer formed by coating and containing microcapsules encapsulating an electron-donating colorless coloring material and a photo-curable composition containing an electron-accepting compound, a polymerizable vinyl monomer, and a photopolymerization initiator outside the microcapsules.
Recording of a color image using such a photosensitive and heat sensitive recording material can be carried out using a recording material comprising a plurality of recording layers having different sensitive light wavelength and coloration hue from one another and disposed on a support.
As a multi-color photosensitive and heat sensitive recording material, for example, the above-described photosensitive and heat sensitive recording materials proposed by the present inventors can be exemplified and more specifically, the proposed recording material comprises a plurality of recording layers which are sensitive to light rays with different wavelengths and different colors, respectively: a first recording layer which is sensitive to light rays with central wavelength λ1 and forms first color, an intermediate layer absorbing light rays with central wavelength λ1, a second recording layer which is sensitive to light rays with central wavelength λ2 and forms second color different from the first color, . . . , an intermediate layer absorbing light rays with central wavelength λi−1, an ith (I≧2) recording layer which is sensitive to light rays with central wavelength λi and forms ith color different from those of the first, the second, . . . , and the (i−1)th recording layers layered in this order in the direction from the exposure light source to the support, with the central wavelength λ at this time λ1<λ2<λi.
Although these recording materials can be used for a variety of purposes, it is impossible to carry out image recording by a light source other than UV rays and short-wavelength visible light rays; i.e., it is impossible to make use of compact, economical infrared lasers, or light rays from blue to red.
Further, in order to permit a high speed and highly accurate image formation, in the case of using such a small and economical infrared laser and light rays covering blue to red color, it is required to introduce a coloring material or the like having absorptivity in the ultraviolet to infrared ray regions into the recording layers. However, if these coloring materials and the like, above all, coloring materials having absorptivity in the visible light region, are used, the background textures are colored and images with low contrast and inferior quality are formed. On the other hand, if a coloring material having absorptivity in the near infrared ray region is used, the coloration of the background textures can be suppressed, yet the used laser is expensive.
On the other hand, as a pressure sensitive recording material, for example, the photosensitive pressure sensitive recording materials disclosed in U.S. Pat. Nos. 4,399,209 and 4,440,846 can be exemplified. Such a recording material contains a dye precursor as an image forming agent in microcapsules and is used for forming a visible image by exposing it imagewise and then evenly applying pressure thereto so as to break the microcapsules in the non-photocured areas and cause reaction of the dye precursor released from the capsules with a developer out of the capsules. As a multi-color recording material of this type, those disclosed in U.S. Pat. Nos. 339,917 and 4,576,891 can be exemplified.
However, in this type of recording materials, since almost all of the compositions to be photocured have photosensitivity in a short wavelength range, similarly to the above-described photosensitive and heat sensitive recording materials, it is impossible to carry out image recording by a light source other than UV rays and short-wavelength visible light rays; i.e., it is impossible to make use of compact, economical infrared lasers, or light rays from blue to red.
Further, when a coloring material having absorptivity in the ultraviolet to infrared ray regions is used in order to make a high speed and highly accurate image formation possible, drawbacks arise in which the background textures are colored and images with low contrast and inferior quality are obtained.